Fuel injector

ABSTRACT

An inwardly opening pressure actuated liquid fuel injector is provided with a valve mounted in an apertured valve guide for reciprocation. The bearing portion of the valve is provided with a pair of longitudinally spaced V-shaped peripheral grooves which are closed by the mating bearing surface of the aperture of the guide and serve to hydraulically center the valve in the aperture and minimize mechanical friction during reciprocation.

nited States Patent 11 1 (Ihapuis 1 1 Mar. 27, 1973 [54] FUEL INJECTOR FOREIGN PATENTS OR APPLICATIONS Inventor: Marcel Chapuis, Versailles, France 571,370 9/1929 Germany .239/535 I 570,842 7/1931 Germany ..239/533 [73] Asslgnee- Inc-1 Hartford 9,5s2 9/1915 Great Britain..-. .239/533 [22] Filed: Sept. 11, 1970 191,305 6/1937 Switzerland ..239/533 447,237 5/1936 Great Britain. .....239/533 [21] Appl. No.: 71,597 129,147 3/1932 Austria ..239/533 I A Primary Examiner-M. Henson Wood,- Jr. 152] U.S. Cl. ...239/533, 239/584, 2513/33/25, Assistant Exqminer Reinhold w. Thieme 51 1111. cr ..F1 6k 21/10 Hayes Kalb [58] Field of Search .....308/5; 92/165; 251/318, 324,

251/282, 214; 137/237 [57] ABSTRACT vAn inwardly opening pressure actuated liquid fuel in- [56] References Cited jector is provided with a valve mounted in an apertured valve guide for reciprocation. The bearing por- UNITED STATES PATENTS tion of the valve is provided with a pairof longitu- 957,286 5 1910 'wilson .251 324 dinally Spaced P Peripheral g o which are 2374 593 4 945 Ems/6181M closed by the mating bearing surface of the aperture 2,627,418 2/1953- Ainsworthw of'the guide and serve'to hydraulically center the 3,596,871 8/1971 Rothrock valve in the aperture and minimize mechanical friction 3,089,627 5/1963 Lippig during reciprocation. 3,348,936 8/1968 De1ano..... 3,425,635 2/1969 4 Claims, 2 Drawing Figures Patented 'March 27, 1973 3,722,801

FIG. 2

INVENTOR. MARCEL CHAFUIS ATTORNEYS FUEL INJECTOR Each measured charge of pressurized fuel is discharged from the injector into a combustion chamber of an associatedengine to operate the engine at the desired speed and torque, and the delivery of fuel tothe injector, and its discharge therefrom, is timed to take place at a predetermined time during the compression strokeof the piston in the associated cylinder.

It is important that the injector discharge the-fuel in afine atomized spray. To produce such an atomized spray, the valveof the injector must be free to chatter", that is, to reciprocate rapidly and frequently between an open and closed position during each injection period. In order to accomplish this, it is essential that the valve be free floating in its guide to avoid seizure or erratic operation of the valve in its guide under all operating conditions and throughout the entire life of the injector.

Accordingly, a primary object of the present invention is to provide an improved injector of the type described having reduced susceptibility to seizure of the valve and related malfunctions under all operating conditions. Included in this object is the provision of means to minimize variations in themechanical friction acting on the valve during reciprocation. J

A further object of this invention is the provision of a precision fuel injector of the reciprocating valve type which is economical to manufacture and reliable in useQ A still further object of this invention is to provide an injector for a compression-ignition engine wherein the valve is hydraulically centered in its supporting guide. Included in this object is the provision of means for assuring a film of lubricant around the entire periphery of the guide portion of the valve.

Another object of this invention is the provision of an injector design resulting in consistent chatter between different injectors and between injectors used with different supply pumps and engines.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements and. arrangement of parts which will be exemplified in the construction hereafter set forth.

In the drawing:

FIG. 1 is a cross-sectional view of a portion of a fuel injector embodying the present invention; and

FIG. 2 is an enlarged fragmentary view of the guide portion of the valve of the injector of FIG. 1.

Referring to the drawing, in which like numerals refer to'like parts throughout the severalviews, the exemplary injector shown herein and embodying the present invention is generally similar to that illustrated in the aforementioned U.S. Pat. No, 3,224,684 and includes an elongated generally tubular body having an apertured tip 12 fixed at one end thereof and a central longitudinal bore 14 extending throughout its length. Located within the central bore 14 is a plunger or valve 16 having a conical tip which cooperates with a conical valve seat 18 formed in the tip 12 to control thedischarge of fuel from the injector. A valve guide 20 is shown as being fixedly positioned within the bore 14 of the body 10 at a position remote from the valve seat to slidably mount the valve 16 and position it in coaxial alignment with the valve seat 18.

The injector is provided with a fuel inlet 24 communicating with a bore 14 of the tubular body 10 for delivery of discrete measured charges of high pressure fuel thereto from a source (not shown). A spring 26 disposed in aspring chamber 28 above valve guide 20 biases the valve 16 downwardly against the seat with a .pressure which may be adjusted by a threaded retainer sleeve 34 received within the end of the tubular body 10' and locked in adjusted position by a lock nut 36. An adjustable lift stop 40 is also provided for limiting the lift of the valve 16 from the valve seat 18.

' When each discrete charge of pressurized fuel delivered to the inlet 24 of the injector increases the pressure of the fuel within the bore 14 to a level to overcome the bias of spring 26, the valve 16 is moved upwardly away from the valve seat 18 and the charge of fuel is discharged through the orifices in the valve tip 12.

As mentioned above, it is important forthe smooth operation of the fuel injector that the plunger 16 be free at all times during the injection period to may cause binding or seizure of the valve 16 in the I valve guide 20. v

"As shown in FIG. 1, a pair of annular recesses are provided between the bearing surfaces of the valve guide 20 and those of the guide portion 16a of the valve 16. As shown, the recesses are provided by forming a pair of longitudinally spaced peripheral grooves 50, 52 on the external surface of the valve 16 with the grooves being disposed intermediate the ends of the valve guide 20 so that the mating bearing surface of valve guide 20 overlies the grooves at all times during operation.

Referring particularly to FIG. 2, the grooves 50, 52 are shown as being substantially V-shaped in cross section with an included angle of about A valve provided with such grooves 50, 52 spaced longitudinally about mils apart with the grooves being about 5-15 and debris accumulation which might otherwise occur as a result of solid particulate contaminants in the fuel.

It has been found that the provision of the double groove construction as described results in valves which will meet the requirements for chattering with a high degree of uniformity from injector toinjector and from engine to engine with the result that the rejection rate of injectors provided with such grooves is one-sixth or less than the rejection rate of identical injectors not provided with the grooves.

In a 4-cycle compression ignition engine, the period generally available for the injection of the charge of.

fuel during each compression stroke is approximately 20 out of every 720 of crank shaft rotation. When such an engine is operating at, say, 3,000 rpm, the period of time for injection of a charge of fuel is about 0.01 l 1 second. It will be readily apparent that the high, short-term pressures encountered within the bore 14 of the injector during the injection period for such an engine create high differential pressure relative to the pressure in spring chamber 28 which is vented by a bleed passage 42. While the guide portion 16a of the valve 16 and the mating surface of the guide 20' are precision sized to minimize leakage into the spring chamber 28 during the injection period, it is apparent that a small amount of leakage willoccur. Moreover, the rapidity of the build-up and dissipation of high pressure within the bore 14 during the injection period will also create transient differential pressures within the bore 14 due to hydraulic shock waves and hydraulic inertia. Such transient differential .pressures adjacent the guide 20 may establish lateral forces on the valve 16 which bias the valve laterally. Such a condition is selfgenerating since it results in a greater clearance (and less resistance for leakage flow) on one side of the valve than on the opposite side. This invention minimizes the effects of this condition by providing for the relatively unimpeded flow of lubricant around the periphery of the valve guide portion 160 through the use of grooves 50, 52. This serves to centralize the valve and reduce the mechanical friction between the valve 16'and the valve guide 20 by promoting a uniform layer of lubricant around the valve guide portion 16a. I

Moreover, the rapid reciprocation of the valve during the injection period to provide the desired chatter, coupled with the tapered shape of the grooves in the direction of reciprocation, establishesan outward'coinponent of force on the fuel in the grooves 50, '52 to bias the fuel against the bearing surface 'of the guide 20 overlying the grooves 50, 52. This assists in promoting the establishment and maintenance of a uniform layer of lubricating film around the entire periphery of the valve portion 16a thereby offering additional assurance that any tendency of the binding or seizure of the charge is minimized.

From the foregoing it will be apparent that the present invention provides a new and improved inwardly opening pressure actuated injector which substantially aids in promoting the uniformity in the atomization of the fuel discharged therefrom by reducing the possibility for seizure or increased mechanical friction between the valve and its guide.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

1 claim:

1. A liquid fuel injector for injecting into the combustion chamber of an associated engine pulsed charges of liquid fuel received from a high pressure fuel source comprising a tubular body having a bore provided with a valve seat and a discharge tip at one end thereof, a pressure-operated inwardly opening valve disposed in said bore, biasing means for biasing said valve toward said valve seat, an apertured valve guide closing the end of said bore remote from said valve seat, said valve having a bearing portion positioned in the aperture of said valve guide tomount said valve for high speed reciprocating movement toward and away from the valve seat, during each injection period of the valve, and means comprising longitudinally spaced peripheral grooves on said bearing portion of said 

1. A liquid fuel injector for injecting into the combustion chamber of an associated engine pulsed charges of liquid fuel received from a high pressure fuel source comprising a tubular body having a bore provided with a valve seat and a discharge tip at one end thereof, a pressure-operated inwardly opening valve disposed in said bore, biasing means for biasing said valve toward said valve seat, an apertured valve guide closing the end of said bore remote from said valve seat, said valve having a bearing portion positioned in the aperture of said valve guide to mount said valve for high speed reciprocating movement towArd and away from the valve seat, during each injection period of the valve, and means comprising longitudinally spaced peripheral grooves on said bearing portion of said valve, said grooves being V-shaped in axial cross section to wedge said valve bearing portion to a center position during such high speed reciprocating movement thereby to overcome lateral forces which may cause binding or seizing of the valve.
 2. The injector of claim 1 wherein the included angle of said V-shaped grooves is of the order of 60* .
 3. The injector of claim 2 in which said grooves are of the order of 10 mils deep.
 4. The injector of claim 1 wherein a groove is disposed adjacent each end of the valve guide. 